The shadow home secretary insisted a “more feminist approach” is needed for the economy to ensure work fits around families as she attempted to pitch herself as the radical and credible candidate.

Speaking in Manchester, Ms Cooper said she did not dismiss the values and intentions of veteran left-winger Mr Corbyn and his supporters.

But she said she would not “pander” to them either and claim to be a “more electable version” of what they stand for.

Ms Cooper, who accepted her attack may lose her votes, said: “Because the truth is that Jeremy is offering old solutions to old problems, not new answers to the problems of today.

“We have to look the 21st century in the eye, face up to the future - that’s where we will find the new radicalism, the answers in the modern fight for social justice, for equality and for solidarity, not in the old answers of the past.

“I understand Jeremy has strong support. But I feel really strongly, not just as a leadership candidate but as a Labour Party member that desperately wants an effective Labour government, that his are the wrong answers for the future - that they aren’t radical and they aren’t credible.

“And they won’t change the world, they will keep us out of power and stop us changing the world.”